Homebrew PCBs

Hi Gang,
        I was wondering if any of you have done a ground plane
on a board. When I mill boards I can use the surrounding copper
as a ground. With Eagle and other programs I can't find a way to
keep the extra copper around the traces. I know I can use the other
side of the board for a ground. I really wanted to stick with a 
single sided boards.
                                          Regards  

                                           John